Snap-fit caps or caps threaded onto glass and plastic bottles and the like are ubiquitous in the bottling industry. Commonly, a closure cap is made of a plastic material and a resilient liner for providing a tight seal. The closure cap includes a planar crown and a depending skirt, with the liner being adhered to the planar crown.
Devices for adhesively attaching the sealing liner to the closure cap are known. U.S. Pat. No. 4,280,864 to Bromberg teaches an apparatus and method for lining caps. Such devices are used on automated assembly lines to apply adhesive to the inside surface of the closure cap, whereafter the sealing liner is brought into pressure contact with the adhesive. The assembled container closure is then releasably fitted to a plastic bottle or the like.
Direct depositing of adhesive onto an interior surface as taught by Bromberg, and squirting of adhesive are two methods of applying a desired pattern onto a closure cap. Both of these methods, however, are susceptible to adhesive tailing resulting from the viscosity of the adhesive which exhibits itself as the cohesion between the molecules of the material extruded from a nozzle and the material remaining at the outlet of the nozzle. Cohesion causes an elongation, commonly referred to as tailing or stringing, after each application of material. A second problem related to tailing is adhesion by the contact of the applied material to a metallic nozzle. Like cohesion, nozzle adhesion causes an elongation of the material.
In most instances tailing is not harmful. Where a dot of adhesive is the desired pattern for bonding a sealing liner to a closure cap, viscous forces merely give the dot a droplet form. However, in automated assembly line use, a nozzle must repeatedly and rapidly extrude the desired pattern. Over a period of time the tailing after some extrusions is excessive, resulting in a filament of adhesive. The filament is referred to as "angel hair" and is undesirable. Filaments which remain attached at one end to the desired pattern of adhesive may drape across the container-engaging threads of the closure cap, causing problems at some later time. Filaments which break away from the desired pattern entirely may become airborne and uncontrolled.
It is an object of the present invention to provide an apparatus and method to protect against the detrimental effects of a nozzle's tailing at the cutoff of adhesive from the nozzle.